1. Field of the Invention
The present invention relates to a one-way clutch used as parts such as those for backstop and torque transmission in the driving apparatus of, for example, an automobile and an industrial machine.
2. Description of the Related Art
In general, a one-way clutch is provided with an outer race, an inner race which is arranged concentrically with the outer race, a plurality of rollers which are arranged between the inner race and the outer race to transmit a torque, a cage which retains the rollers, and spring members which urge the rollers in the direction in which the rollers engage with a cam face of the outer race or the inner race.
In such an arrangement, the one-way clutch is such that due to a cam mechanism including the rollers and the cam face, in a case where the cam face is provided in the outer race, the inner race is rotated only in a single direction with respect to the outer race. That is, the inner race runs idle in one direction with respect to the outer race and can give a rotary torque to the outer race in the reverse direction alone through the cam mechanism. At this time, the rollers are urged in the meshing direction (engaging direction) by urging members such as springs.
In the one-way clutch disclosed in Japanese Patent Application Laid-Open No. 2008-261488, for example, accordion springs are used as spring members which urge the rollers in the direction in which the rollers engage with the cam face of the outer race or the inner race.
However, when accordion springs are used, it is necessary that holes or concavities for mounting be formed in the outer race or the inner race, posing the problem that it is impossible to reduce costs. Also, mounting methods are relatively complicated, posing another problem that the stress concentration at a maximum contraction is relatively high. Similar problems occurred also with coil springs.
In particular, embrittlement may occur under impact and load because of the relatively high stress concentration at a maximum contraction, with the result that the roller urging force becomes unstable, leading to unstable operations of the one-way clutch.